Material having a damping property and masterbatch pellets therefor

ABSTRACT

The disclosure described a material having a damping property, comprising 100 parts by weight of a binder resin composed of 85 to 99% by weight of at least one base resin selected from the group consisting of polypropylenes, polystyrenes, acrylonitrile-butadiene-styrene copolymers, polycarbonates, polyphenylene ethers and modified polyphenylene ethers and 1 to 15% by weight of styrene-isoprene-styrene block copolymer, and 1 to 20 parts by weight of iron compound particles.

This is a Rule 62 File Wrapper Continuation of application Ser. No.08/496,914, filed Jun. 29, 1995, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a material having a damping propertyand masterbatch pellets used for production thereof. More particularly,the present invention relates to a material having a damping propertywhich shows a high internal loss at around room temperature and has asufficient strength and hardness. The material having a damping property(hereinafter referred to as "damping material") of the present inventionis mainly used as structural materials of electrical or electronicequipments, casings or bodices of household electric appliances ofoffice automation equipments, parts of various kinds of machines andapparatus, interior parts of vehicles and ships, building materials andthe like. It finds particularly useful application to a cartridge halfand a cassette half.

As is well known, a damping material is widely used in many fields ofindustry for the purpose of damping vibration or noise generated fromvarious sources and occasions, for example, vibration or noise which isgenerated incidental to operation of engine or motor mounted in variouskinds of machines and apparatus, for instance, office automationequipments, household electric appliances such as washing machines,dryer, etc., a cartridge half and cassette half of data cartridge tapes,video tapes, audio tapes, etc., disk shells of optical discs,magneto-optical discs, magnetic discs, acoustic optical discs, etc.,acoustic equipments, precision machine tools, works plant equipments,and various kinds of vehicles and ships; vibration or noise generatedfrom piping such as water and gas pipes in buildings, ducts of airconditioning systems, etc.; and vibration or noise generated fromrunning of vehicles on road or railway tracks.

The damping material is usually offered as a sheet-like material orblock-like material produced by kneading and molding a binder resin andfiller material such as mica, iron oxide or the like by a suitablemolding method such as extrusion molding, calender molding, compressionmolding, injection molding or cast molding, or it is provided directlyas a structural material of electrical or electronic equipments, casingsof household electric appliances, office automation equipments, acartridge half and a cassette half, etc. Namely, as for the using modeof the damping material, it may be used so that a molded sheet-likematerial or block-like material is stuck to or put between pertinentsection(s) of an objective apparatus, etc., or it may be directlyapplied as a structural material of electrical or electronic equipments,casings of household electric appliances, office automation equipments,a cartridge half, a cassette half, etc.

Recently, there is seen a remarkable trend toward the miniaturizationand lightweight of handy apparatus such as office automation equipmentsand acoustic equipments, and a damping material used in such machines,equipments, appliances and tools has been strongly required tominiaturize and reduce the weight. To meet this requirements, thedamping material is demanded to have a high damping property, that is, ahigh internal loss. However, if it is simply tried to increase theamount of inorganic filler material used in the damping material for theonly purpose of improving damping property, it invites a reduction ofstrength and hardness of rigid resin used as binder resin, andmoldability of the material is impaired. Further, since specific gravityof the produced damping material elevates, this runs counter to therequirements of the miniaturization and lightweight. It is thus stronglyrequired of damping material to have an excellent damping property whilemaintaining an intrinsic strength (e.g. bending strength) and hardnessof a rigid resin. This fact is referred to in, for instance, JapanesePatent Application Laid-open (KOKAI) No. 4-45142 which states: "Asthermoplastic resin composition having damping properties, there areknown compositions obtained by blending a large amount of fillermaterial such as calcium carbonate with polypropylene. Thesecompositions, however, had the disadvantages in that the intrinsicpriorities of resin (such as good moldability and high impact strength)are deteriorated because of blending of a large amount of fillermaterial. Development of a damping materiel capable of retaining theintrinsic properties of resin has, therefore, been desired."

Recently, large numbers of the movable parts such as motors, relays,transforms, gears, cums, gear boxes and the like, and the electrical,electronic or machine parts which generate vibration and/or noise areused in the household electric appliances or the office automationequipments. The vibration generated from such parts is transferred toother parts and/or casings, and as a result, the intended performancesof the product can not be exhibited. According to circumstances, it maybe invite to malfunction and/or generate unpleasant vibration. So, thedamping material used as a structural material of the electrical,electronic or machine parts, and the casings of the household electricappliances or the office automation equipments is strongly required tohave a sufficiently high strength and hardness, and excellent internalloss at around room temperature (e. g., 20 to 28° C.).

Also, in recording media such as optical disks or magnetic disks used incomputers, word processors and the like, data-cartridge tapes, video andaudio optical disks, cassette tapes, etc., higher reliability, tonequality and picture quality of the recording media are stronglydemanded.

These recording media are set in a recorder and driven to run by a motoror other motive force to make recording or reading-out. Vibrationgenerated in the inside of the cartridge half or cassette half (forexample, vibration caused by "play" around a shaft such as hub fortaking up the magnetic tape) or vibration from a source outside thecartridge half or cassette half (for example, vibration caused byoperation of motor) exerts baneful influence on recording andreading-out, so that it is difficult to have accurate recording andreading-out of information. Therefore, the damping material used as astructural material for cartridge half or cassette half is stronglyrequired to satisfy the above requirement, i.e., to have an excellentinternal loss at around room temperature while maintaining high strengthand hardness.

As binder resin for damping material, there are usually usedthermoplastic resins (rigid resins) such as polypropylenes,polystyrenes, acrylonitrile-butadiene-styrene copolymers,polycarbonates, polyphenylene ethers, modified polyphenylene ethers andthe like. These rigid resins are preferably used because of relativelylow cost and excellent molding workability.

These rigid resins, however, are not satisfactorily excellent ininternal loss at around room temperature.

Many attempts have been made for improving a damping property of theserigid resins. For instance, Japanese Patent Application Laid-open(KOKAI) No. 2-3-00250 proposes a polypropylene composition improved in adamping property obtained by incorporating a styrene-isoprene-styreneblock copolymer in polypropylene resin. Japanese Patent ApplicationLaid-open (KOKAI) No. 3-45646 proposes an ABS resin composition havingimproved damping property, obtained by incorporating astyrene-isoprene-styrene copolymer to an acrylonitrile-butadiene-styrenecopolymer. Japanese Patent Application Laid-open (KOKAI) No. 3-181552proposes a polyphenylene ether resin composition having excellentdamping properties, comprising a polyphenylene ether and astyrene-isoprene-styrene block copolymer. Japanese Patent ApplicationLaid-open (KOKAI).No. 5-70699 proposes a thermoplastic resin compositionwith improved damping property, obtained by incorporating astyrene-isoprene-styrene block copolymer in a thermoplastic resin. Also,in Japanese Patent Application Laid-open (KOKAI) No. 5-59234 is proposeda damping material resin composed of polypropylene and astyrene-isoprene-styrene block copolymer.

More specifically, Japanese KOKAI No. 2-300250 discloses a polypropylenecomposition comprising (a) 97-50 parts by weight of polypropylene and(b) 3-50 parts by weight of a block copolymer having a number-averagemolecular weight of 30,000-300,000 or a hydrogenation product thereof,the said block copolymer composed of blocks (A) comprising an aromaticvinyl monomer having a number-average molecular weight of 2,500-40,000and blocks (B) comprising isoprene or an isoprene-butadiene mixture,whose number-average molecular weight is 10,000-200,000 and 3,4 bond and1,2 bond content is 40% or more, and which shows a peak of maindispersion of tan δ at 0° C. or more.

The problem to be solved by Japanese KOKAI No. 2-300250 is to reducevibration and noise at around room temperature in the range wherevarious kinds of the equipments and appliances are practically used.

Japanese KOKAI No. 3-45646 discloses an ABS resin composition comprising(a) 97-50 parts by weight of an ABS resin and (b) 3-50 parts by weightof a block copolymer having a number-average molecular weight of30,000-300,000 or a hydrogenation product thereof, the said blockcopolymer composed of blocks (A) comprising an aromatic vinyl monomerhaving a number-average molecular weight of 2,500-40,000 and blocks (B)comprising isoprene or an isoprene-butadiene mixture, having anumber-average molecular weight of 10,000-200,000 and a 3,4 bond and 1,2bond content of 40% or more and showing a peak of main dispersion of tanδ at 0° C. or more.

The object of Japanese KOKAI No. 3-45646 is to improve a dampingproperty at around room temperature in the widely used ABS resin fordamping material in various kinds of the equipments and appliances.

Japanese KOKAI No. 3-181552 discloses a polyphenylene ether resincomposition comprising (a) 97-50 parts by weight of polyphenylene etherand (b) 3-50 parts by weight of a block copolymer having anumber-average molecular weight of 30,000-300,000 or a hydrogenationproduct thereof, the said block copolymer composed of blocks (A)comprising an aromatic vinyl monomer having a number-average molecularweight of 2,500-40,000 and blocks (B)comprising isoprene or anisoprene-butadiene mixture, having a number-average molecular weight of10,000-200,000 and a 3,4-bond and 1,2-bond content of 40% or more andshowing a peak of main dispersion of tan δ at 0° C. or more.

Japanese KOKAI No. 5-70699 discloses a thermoplastic resin compositioncomprising (a) 97-50 parts by weight of a thermoplastic resin and (b)3-50 parts by weight of a block copolymer having a number-averagemolecular weight of 30,000-300,000 or a hydrogenation product thereof,said block copolymer composed of blocks (A) comprising an aromatic vinylmonomer having a number-average molecular weight is 2,500-40,000 andblocks (B) comprising isoprene or an isoprene-butadiene mixture, whosenumber-average molecular weight is 10,000-200,000 and Tg is 0 to 40° C.,wherein said blocks A and B are coupled together in the form ofA(BA)_(n) or (AB)_(n) (n:an integer of 1 or more).

The object of Japanese KOKAI No. 5-70699 is to improve impact resistancein the low temperature region.

The thermoplastic resins proposed in Japanese KOKAI No. 5-70669 includepolyolefins such as polyethylene and polypropylene, polyester such aspolyethylene terephthalate and polybutylene terephthalate, styreneresins such as ABS and AS resins, polyamides, polyphenylene ethers,polyacetals and polycarbonates.

Japanese KOKAI No. 5-59234 discloses a damping material resin comprisinga polypropylene resin composition composed of a mixture of 50-95% byweight of a polypropylene and 5-50% by weight of a thermoplasticelastomer and an inorganic filler, said inorganic filler being blendedin an amount of 10-150 parts by weight based on 100 parts by weight ofsaid resin mixture, wherein said thermoplastic elastomer is composed ofa block polymer of a styrene-isoprene-styrene structure havingpolyisoprene blocks of vinyl structure.

A damping material composition obtained by adding iron oxide particlesas an inorganic filler for improving a damping property is proposed inJapanese Patent Application Laid-open (KOKAI) No. 3-287652. Thecomposition of this KOKAI comprises 100 parts by weight of a blockcopolymer having a number-average molecular weight of 30,000 to 300,000and composed of blocks (A) comprising an aromatic vinyl monomer having anumber-average molecular weight of 2,500 to 40,000, and blocks (B)comprising isoprene or an isoprene-butadiene mixture, having anumber-average molecular weight of 10,000 to 200,000 and a 3,4-bond and1,2-bond content of 40% or more and showing a peak of main dispersion oftan δ at 0° C. or more, and 30 to 1000 parts by weight of iron oxideparticles.

In production of damping materials mainly composed of thermoplasticresins, it has been common practice in the art to add an inorganicfiller material directly to a base resin. However, for better handlingand easier preparation of the composition, there is proposed a processusing masterbatch pellets in which masterbatch pellets are prepared bydispersing an inorganic filler material in a base resin at a higherconcentration than the desired one and these masterbatch pellets aremixed and dispersed in the base resin to adjust the concentration ofinorganic filler to the purposed level thereof.

Accordingly, the masterbatch pellets for the damping material, which areeasy to handle in producing the damping material and capable ofaffording a satisfactory damping effect with a moderate amount ofaddition thereof, are also required.

A damping material having an excellent internal loss in the commonlyused temperature range, particularly at around room temperature (forexample, 20 to 28° C.), while maintaining a satisfactorily high strengthand hardness of a rigid resin, is most strongly required at present, butnone of the damping materials of the prior art mentioned above is unableto well satisfy the said requirements.

Any of the damping materials disclosed in the above-mentioned JapaneseKOKAIs No. 2-300250, No. 3-45646, No. 3-181552, No. 5-70699 and No.5-59234 is unsatisfactory in a damping property because of non-use ofiron oxide particles as inorganic filler and also incapable ofmaintaining an intrinsic strength and hardness of a rigid resin becauseof high content of an inorganic filler.

The damping material disclosed in Japanese KOKAI No. 3-287652 mentionedabove has an excellent damping property in the practical temperaturerange from room temperature to high temperature but is low in strength,that is, this damping material is low in bending modulus.

The problem to be solved by the present invention is to provide adamping material having an excellent internal loss in the practicaltemperature range, particularly at around room temperature, whilemaintaining the intrinsic strength and hardness of rigid resin.

As a result of the present inventors' earnest studies for solving theabove-mentioned problem, it has been found that by preparing masterbatchpellets from 100 parts by weight of a binder resin composed of not morethan 70% by weight of at least one base resin selected from the groupconsisting of polypropylenes, polystyrenes,acrylonitrile-butadiene-styrene copolymers, polycarbonates,polyphenylene ethers and modified polyphenylene ethers, and not lessthan 30% of styrene-isoprene-styrene block copolymer, and 50 to 300parts by weight of iron compound particles, adding 70 to 99% by weightof at least one base resin selected from polypropylenes, polystyrenes,acryl onitrile-butadiene-styrene copolymers, polycarbonates,polyphenylene ethers and modified polyphenylene ethers to 1 to 30% byweight of said masterbatch pellets, and after kneading, molding theresultant mixture, the obtained damping material composed of 100 partsby weight of a binder resin composed of 85 to 99% by weight of at leastone base resin selected from polypropylenes,. polystyrenes,acrylonitrile-butadiene-styrene copolymer, polycarbonates, polyphenyleneethers and modified polyphenylene ethers and 1 to 15% by weight ofstyrene-isoprene-styrene block copolymers, and 1 to 20 parts by weightof iron compound particles, has an excellent internal loss at aroundroom temperature, and high strength and hardness. The present inventionhas been attained on the basis of this finding.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a damping materialhaving an excellent internal loss at around room temperature, andsatisfactory strength and hardness

To attain the aim, in the first aspect of the present invention, thereis provided a damping material comprising 100 parts by weight of binderresin composed of 85 to 99% by weight of at least one base resinselected from polypropylenes, polystyrenes,acrylonitrile-butadiene-styrene copolymers, polycarbonates,polyphenylene ethers and modified polyphenylene ethers and 1 to 15% byweight of styrene-isoprene-styrene block copolymer, and 1 to 20 parts byweight of iron compound particles.

DETAILED DESCRIPTION OF THE INVENTION

The damping material according to the present invention has a lossfactor of not less than 0.015, preferably not less than 0.020 at atemperature of 24° C. and a relative bending modulus of not less than70%, preferably not less than 75% based on a bending modulus of adamping material consisting of the base resin, which show that theinternal loss at around room temperature is excellent and the intrinsicstrength and hardness of rigid resin is fully maintained.

As base resin used in the present invention, one or more of the resinsselected from the group consisting of polypropylenes, polystyrenes,acrylonitrile-butadiene-styrene copolymers, polycarbonates,polyphenylene ethers and modified polyphenylene ethers can be used. Theamount of the base resin used is 85 to 99% by weight, preferably 88 to98% by weight based on the binder resin. When the amount of the baseresin exceeds 99% by weight, there can not be obtained the desiredeffect of improving the damping property because of too small content ofstyrene-isoprene-styrene block copolymer in the binder resin. When theamount of the base resin is less than 85% by weight, the strength andhardness of the base resin, specifically the bending modulus thereof islowered because of too large content of styrene-isoprene-styrene blockcopolymer in the binder resin, and thus it is impossible to maintain theintrinsic strength of the base resin and to provide the damping materialof the desired bending modulus and hardness.

As polypropylenes usable in the present invention, homopolypropylenes,propylene copolymers such as propylene-ethylene random copolymer(ethylene content being not more than 20% by weight) andpropylene-ethylene block copolymer (ethylene content being not more than20% by weight), and polypropylenes modified with an unsaturatedcarboxylic acid or derivatives thereof may be exemplified.

Acrylonitrile-butadiene-styrene copolymers used in the present inventionare of a composition of 20 to 30 wt % of acrylonitrile, 10 to 30 wt % ofbutadiene and 40 to 70 wt % of styrene.

As polystyrenes used in the present invention, available polystyrenesincluding homopolystyrenes and copolymers such as polystyrene-butadienecopolymers, etc. can be cited. As the polystyrene-butadiene copolymers,a high-impact polystyrene (HI-PS) obtained by graft-polymerizing styreneto butadiene rubber may be exemplified.

Polycarbonates used in the present invention are preferably one having aviscosity-average molecular weight of 1.8×10⁴ to 3.3×10⁴. Suchpolycarbonates are commercially available under the trade names ofNovalex (produced by Mitsubishi Chemical Co., Ltd.), Panlight (producedby Teiji Chemical Co., Ltd.), Yupiron (Produced by Mitsubishi GasChemical Co., Ltd.), Taflon (produced by Idemitsu Petrochemical Co.,Ltd.), Rexan (produced by General Electric Corp.), Macron (Produced byBayer Corp.), etc.

Examples of polyphenylene ethers usable in the present invention arepoly(2,6-dimethyl-1,4-phenylene) ether, poly(2,6-diethyl-1,4-phenylene)ether, poly(2-methyl-6-ethyl-1,4-phenylene) ether,poly(2-methyl-6-propyl-1,4-phenylene) ether,poly(2,6-dipropyl-1,4-phenylene) ether, andpoly(2-ethyl-6-propyl-1,4-phenylene) ether.

Modified polyphenylene ethers usable in the present invention is apolymer alloy of polyphenylene ether and styrene-based resin (Norylresin, produced by General Electric Corp.) and a polymer alloy ofpolyphenylene ether and polyamide resin (Noryl GTYX resin, produced byGeneral Electric Corp.).

As a base resin, polystyrenes, acrylonitrile-butadiene-styrenecopolymers, polycarbonates, polyphenylene ethers and modifiedpolyphenylene ethers are preferably used in the present invention.

Styrene blocks in the styrene-isoprene-styrene block copolymer used inthe present invention are constituted by an aromatic vinyl monomercapable of anionic polymerization, such as styrene, 1-vinylnaphthalene,2-vinylnaphthalene, 3-methylstyrene, 4-propylstyrene,4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene,4-phenylbutylstyrene and the like. Among them, styrene is especiallypreferred.

Isoprene blocks in the said styrene-isoprene-styrene block copolymer arepreferably constituted by isoprene or isoprene-butadiene. In case othermonomers are used, for instance, if butadiene alone is used, thetemperature at which a damping effect is produced is below 0° C. even ifthe content of vinyl bonds is increased, and the desired dampingproperty cannot be obtained in the practical temperature range. In thiscase, therefore, the damping material can be applied to a wide scope ofuse and has a very high practical significance. When isoprene-butadieneis used, the desired damping property can be obtained in the temperaturerange not less than 0° C. in case of isoprene being not less than 40%.As the isoprene-butadiene copolymers, random, block or taperedcopolymers are usable.

Number-average molecular weight of the obtained styrene-isoprene-styreneblock copolymer is in the range of 30,000 to 300,000. When the molecularweight is less than 30,000, the mechanical properties such as strengthand elongation at breaking of the block copolymer itself aredeteriorated, resulting in a reduced strength of the damping material.When the molecular weight exceeds 300,000, the workability thereofworsened. Thus, the preferred range of the molecular weight (Mn) of thesaid block copolymers is from 80,000 to 250,000.

The block formation in the said styrene-isoprene-styrene blockcopolymers is A(BA)_(n) or (AB)_(n), wherein A represents styrene block,B represents isoprene block, and n is an integer of 1 or more. Theformation of A(BA)_(n) is preferred.

The content of the styrene-isoprene-styrene block copolymers in thebinder resin is in the range of 1 to 15% by weight, preferably 2 to 12 %by weight. When the content is less than 1% by weight, the desiredimprovement of damping properties can not be obtained due to diffusionof the said block copolymers in the base resin. When the content exceeds15% by weight, the strength and hardness of the base resin is lowered,thereby making it unable to maintain the intrinsic strength and hardnessof the base resin.

As iron compound particles in the present invention, there can be usedhematite particles, maghemite particles, magnetite particles,Berthollide compounds particles and hard ferrite particles such asstrontium ferrite particles and barium ferrite particles, and hydrousiron oxide particles such as goethite (α-FeOOH) particles, akaganeite(β-FeOOH) particles, lepidocrosite (γ-FeOOH) particles and the like.Among them, magnetite particles, strontium ferrite particles and bariumferrite particles are preferred. The preferred BET specific surface ofthe magnetite particles is 3 to 40 m² /g and the BET specific surfacethe barium ferrite particles or strontium ferrite particles is 0-3 to 20m² /g. The shape thereof is not limited, and it may be, for instance,granular, spindle, acicular, plate-like or the like. The granular shapeis preferred. The average particle size of the iron compound particlesusable in the present invention is in the range of 0.05 to 10 μm. It ispreferable in the range of 0.1 to 5 μm due to advantageous in terms ofproperties of the damping material and economy.

The amount of iron compound particles used in the present invention is 1to 20 parts by weight based on 100 parts by weight of the binder resin.When the amount is less than 1 part by weight, the desired excellentinternal loss can not be obtained. When the amount exceeds 20 parts byweight, the bending modulus which is an index of strength of rigidresin, lowers to make it unable to obtain a satisfactory strength of thedamping material. Also, specific gravity of the damping materialincreases, thereby vitiating the advantage of the resin of beinglightweight The preferred content of iron compound particles is 3 to 20parts by weight based on 100 parts by weight of the binder resin.

The damping material according to the present invention comprises thebase resin, the styrene-isoprene-styrene block copolymer and the ironcompound particles as essential components, but if necessary, otherpolymer(s), compatilizing agent, oxidation stabilizer, etc., may beblended within the range which does not impair the purpose of thepresent invention. For instance, polymers such as natural rubbers (NR),isoprene rubbers (IR), butadiene rubbers (BR), styrene-butadiene rubbers(SBR), ethylene-propylene-diene terpolymars (EPDM), ethylene-propylenerubbers (EPR), styrene-conjugated diene block copolymers andhydrogenation product thereof may be blended. The amount of the polymeris not more than 30 parts by weight, preferably in the range of 5 to 25parts by weight based on 100 parts by weight of the binder resin.

For producing the damping material according to the present invention,masterbatch pellets for damping material described later and the baseresin composed of at least one resin selected from the group consistingof polypropylenes, polystyrenes, acrylonitrile-butadiene-styrenecopolymers, polycarbonates, polyphenylene ethers and modifiedpolyphenylene ethers are mixed by a suitable mixer such as Ribbonblender, Nauta mixer, Henschel mixer or Supermixer, and the resultantmixture is molded into the objective product by a suitable moldingmachine such as injection molding machine.

The masterbatch pellets for the damping material according to thepresent invention have a grain size of 1 to 10 mm, preferably 3 to 7 mm.When the grain size of pellets is less than 1 mm, the workability is badin the production of pellets, while when the grain size exceeds 10 mm,it becomes difficult to disperse the pellets in base resin.

The grain shape is not specified, but it may be, for instance,indeterminate, columnar, spherical, flaky and the like.

As the base resin of the said masterbatch pellets, at least one resinselected from the group consisting of polypropylenes, polystyrenes,acrylonitrile-butadiene-styrene copolymers, polycarbonates,polyphenylene ethers and modified polyphenylene ethers is used in anamount of not more than 70% by weight, preferably in the range of notmore than 65% by weight based on the binder resin. When the amount ofthe base resin exceeds 70% by weight, it is difficult to obtain thedesired concentration of styrene-isoprene-styrene block copolymer resinin production of damping material because of small content ofstyrene-isoprene-styrene block copolymer.

The composition of base resin in the masterbatch pellets may be the samecombination of resins as base resin to be mixed with masterbatchpellets, or may be a different combination of the resins.

As styrene-isoprene-styrene block copolymer resin in the masterbatchpellets, there can be used the resins mentioned above and the amountthereof added is 30 to 100% by weight, preferably 35 to 100% by weightbased on the binder resin of the masterbatch pellets. If the amount ofthis resin is less than 30% by weight, it is undesirable since theamount of masterbatch pellets necessary for producing the dampingmaterial increases.

As iron compound particles of the masterbatch pellets, those mentionedabove can be used and the amount of the iron compound particles is 50 to300 parts by weight, preferably 60 to 250 parts by weight based on 100parts by weight of the binder resin. If the amount of the iron compoundparticles is less than 50 parts by weight, the amount of the masterbatchpellets necessary for producing the damping material increases. If theamount of the iron compound particles exceeds 300 parts by weight, itbecomes difficult to adjust the content of the iron compound particlesto a desired level since their content in the damping material is variedgreatly by a slight change of the amount of the masterbatch pelletsadded. This is also causative of extensive mechanical abrasion.

The masterbatch pellets for the damping material according to thepresent invention are produced by mixing styrene-isoprene-styrene blockcopolymers and iron compound particles with base resin selected frompolypropylenes, polystyrenes, acrylonitrile-butadiene-styrene copolymer,polycarbonates, polyphenylene ethers and modified polyphenylene ethersby a suitable mixing machine such as Ribbon blender, Nauta mixer,Henschel mixer, Supermixer or the like, and kneading and molding theresultant mixture by a known single-screw or twin-screw extruder, andcutting the molded product, or pulverizing and molding the resultantmixture kneaded by a Banbury mixer, press kneader or the like andcutting the molded product, thereby obtaining the desired granularmaterial.

The damping material according to the present invention is produced byadding 1 to 30% by weight of the said masterbatch pellets to 70 to 99%by weight, preferably 75 to 95% by weight of the base resin comprisingat least one resin selected from the group consisting of polypropylenes,polystyrenes, acrylonitrile-butadiene-styrene copolymers,polycarbonates, polyphenylene ethers and modified polyphenylene ethers,and kneading and molding the resultant mixture. The preferable amount ofthe masterbatch pellets added 5 to 25% by weight, more preferably 5 to20% by weight. When the amount of the masterbatch pellets added is lessthan 1% by weight, the effect of addition thereof is too small. When theamount of the masterbatch pellets exceeds of 30% by weight, theintrinsic strength and hardness of base resin may be adversely affected.

The structural materials of electrical or electronic equipments, casingsor bodies of household electric appliances, office automationequipments, etc., a cartridge half, a cassette half and the likeaccording to the present invention are produced from the dampingmaterial of the present invention, and the above-described productionprocess can be employed for the production of the structural materialsof electrical or electronic equipments, casings or bodies of householdelectric appliances, office automation equipments, etc., a cartridgehalf, a cassette half and the like.

The structural materials of electrical or electronic equipments, casingsor bodies of household electric appliances, office automationequipments, etc., a cartridge half, a cassette half and the likeaccording to the present invention have a loss factor of not less than0.015, preferably not less than 0.020 at an-ordinary temperature (24°C.), and a relative bending modulus of not less than 70%, preferably notless than 75% based on a bending modulus of structural materials,casings, a cartridge half, a cassette half made of only the base resin.

The fact that a damping material having an excellent internal loss inthe practical temperature range, especially at around room temperature,while maintaining the intrinsic strength and hardness of rigid resin canbe obtained according to the present invention may be accounted for bythe followings.

It is considered that in the damping material according to the presentinvention, styrene-isoprene-styrene block copolymer is dispersed, in theform of fine lumps, in the base resin comprising at least one resinselected from the group consisting of polypropylenes, polystyrenes,acrylonitrile-butadiene-styrene copolymers, polycarbonates,polyphenylene ethers and modified polyphenylene ethers, and a dampingeffect is produced by friction at the interface between the dispersedfine lumps of styrene-isoprene-styrene block copolymer and the baseresin. The fact is particularly notable that the smaller the size of thesaid dispersed fine lumps, the greater becomes the contact area betweenthe dispersed fine lumps of styrene-isoprene-styrene block copolymer andthe base resin, resulting in a better damping property, that is, higherinternal loss.

However, when the content of styrene-isoprene-styrene copolymer isincreased, although the loss factor elevates, the intrinsic strength andhardness of the rigid resin, specifically its bending modulus, isreduced.

As a result of the present inventors' studies on the subject problem, ithas been found that by using iron compound particles, it is possible toelevate the loss factor more than that of using conventional inorganicfillers such as mica other than iron compound, and by adding a smallamount of styrene-isoprene-styrene block copolymer resin, the efficientenhancement of loss factor can be effected, while suppressing thelowering the strength and hardness of the base resin.

This effect may be attributed to the followings. The lumps ofstyrene-isoprene-styrene block copolymer dispersed in base resin can bemade fine in size due to the iron compound particles, and consequentlythe dispersed state of the lumps thereof becomes finer, therebyelevating the damping effect by friction with the base resin, resultingin an increased loss factor.

By the way, as seen from Comparative Examples 13 and 14 described later,the damping property of the damping material comprising the base resinand iron compound particles dispersed in the base resin without blendingstyrene-isoprene-styrene block copolymer do not improved.

Further, a smaller amount of the iron compound particles than that ofmica or other conventional filler is required for obtaining a same levelof loss factor, and the amount of styrene-isoprene-styrene blockcopolymer to be added can be minimized. As a result, it is consideredthat a damping material showing an excellent internal loss in thepractical temperature range, particularly at around room temperature,while maintaining the intrinsic strength and hardness of the rigidresin, can be obtained.

Thus, according to the present invention, by the synergistic effect ofthe combination and the said specific mixing ratios of (1) base resincomprising at least one resin selected from the group consisting ofpolypropylenes, polystyrenes, acrylonitrile-butadiene-styrenecopolymers, polycarbonates, polyphenylene ethers and modifiedpolyphenylene ethers, preferably at least one resin selected from thegroup consisting of polystyrenes, acrylonitrile-butadiene-styrenecopolymers, polycarbonates, polyphenylene ethers and modifiedpolyphenylene ethers (2) styrene-isoprene-styrene block copolymer, and(3) iron compound particles, such damping material has a loss factor ofnot less than 0.015, preferably not less than 0.020 at an ordinarytemperature (24° C.), a relative bending modulus of not less than 70%,preferably not less than 75% based on a bending modulus of a dampingmaterial consisting of the base resin, and a specific gravity of 0..95to 1.30.

The damping material according to the present invention, as describedparticularly in the Examples given below, has a high internal loss ataround room temperature, while maintaining the intrinsic strength andhardness of rigid resin, so that it is capable of significantminiaturization, lightweight and thinning, and can be effectivelyapplied to structural materials of electrical or electronic equipments,casings or bodies of office automation equipments or household electricappliances, parts of various kinds of machines and apparatus, internalparts of vehicles and ships, building materials, etc., particularlyuseful to cartridge half and cassette half of data cartridge tapes,video tapes, audio tapes etc., disk shell of optical discs,magneto-optical discs, magnetic discs, acoustic optical disc, etc.

EXAMPLES

The present invention will be explained in more detail hereinafter withreference to the following examples and comparative examples.

Loss factor η used as an index of damping property, i.e., loss factor ofthe damping material was determined by injection molding a 200 mm×12.5mm×3 mm test piece and measuring loss factor η of this test piece bycantilever beam-type resonance method under the conditions of 24° C. and1 kHz.

Loss factor η of casing of cassette half, household electric appliancesor office automation equipments was determined in the followings. Thecasing was suspended from two points with a kite string. Then a metalhall (1.05 g in weight and 6 mm in diameter) suspended with a kitestring (250 mm in length) was pulled up to an angle of 60° from thevertical plane with its fulcrum taken vertically above the casing anddropped down to the casing to give vibrations to the central part of thecasing. Transmission of vibrations was detected by a vibration pickupset at the bottom of the casing and data processing was made by FFTAnalyzer 3550 (manufactured by B & K Corp.) under the condition of 24°C. to determine loss factor η.

Bending modulus which is an index of strength of damping material wasdetermined by injection molding a 80 mm×12.5 mm×3 mm test piece andmeasuring bending modulus of this test piece according to ASTM D-790.

Specific gravity was measured by a specific gravity hydrometer(manufactured by EW-120SG, Mirage Trading Co., Ltd.).

<Production of masterbatch pellets for damping material>

EXAMPLE 1

100 parts by weight of binder resin composed of 50 parts by weight ofhigh-impact polystyrene resin (Sumibright M-574, produced by SumitomoChemical Co., Ltd.) and 50 parts by weight of styrene-isoprene-styreneblock copolymer (VS-1, produced by Kuraray Co., Ltd.), and 100 parts byweight of granular magnetite (VD-803C, produced by Toda KogyoCorporation; average particle size: 0.27 μm and BET specific surfacearea: 4.5 m² /g) were kneaded at 160° C. by a twin-screw kneader andextruded from a 3 mmφ die, and the extrudate was cut to theapproximately 3 mm units to obtain masterbatch pellets A.

EXAMPLES 2-9 AND COMPARATIVE EXAMPLES 1-2

The kind and amount of base resin, styrene-isoprene-styrene blockcopolymer and iron oxide particles in the masterbatch pellets wereselected as shown in Table 1 to prepare masterbatch pellets for dampingmaterial B-K.

<Production of damping material>

EXAMPLE 10

90 parts of high-impact polystyrene resin (Sumibright M-574, produced bySumitomo Chemical Co., Ltd.) used as base resin and 10 parts by weightof masterbatch pellets A were uniformly blended by a Henschel mixer andinjection-molded into a strip-shaped test piece. The loss factor η ofthis test piece at an ordinary temperature (24° C.) was 0.021, itsbending modulus was 25,400 kgf/cm² (relative bending modulus: 95%) andits specific gravity was 1.09.

EXAMPLES 11-23 AND COMPARATIVE EXAMPLES 3-9

Samples of damping material were produced by the same procedure asExample 10 except that the kind of masterbatch pellets, the kind of baseresin mixed with masterbatch pellets and the mixing ratios of said baseresin and masterbatch pellets were changed as shown in Table 2. Thecharacteristics of the samples of Examples 11-23 are shown in Table 4,and the characteristics of the samples of Comparative Examples 3-9 areshown in Table 5.

COMPARATIVE EXAMPLES 10-14

Samples of damping material were produced by blending and kneading baseresin, styrene-isoprene-styrene block copolymer and flaky mica withoutusing masterbatch pellets, at the ratios shown in Table 3, and moldingthe mixtures. The characteristics of these samples are shown in Table 5.

EXAMPLE 24

90 parts by weight of high-impact polystyrene resin (Sumibright M-574,produced by Sumitomo Chemical Co., Ltd.) used as base resin and 10 partsby weight of masterbatch pellets A were uniformly blended by a Henschelmixer and injection molded into a cassette half casing (structuralmaterials) The loss factor η of this casing at an ordinary temperature(24° C.) was 0.031.

REFERENCE EXAMPLE 1

Cassette half of a commercial available cassette tape was taken asreference example and its loss factor at an ordinary temperature (24°C.) was determined. It was 0.015.

EXAMPLE 2

93 parts by weight of polycarbonate (Novalex 7025A, produced byMitsubishi Chemical Corporation) used as base resin and 7 parts byweight of masterbatch pellets F were uniformly blended by a Henschelmixer and injection molded into a gear. The loss factor η of this gearat ordinary temperature (24° C.) was 0.021.

REFERENCE EXAMPLE 2

A gear was produced by the same procedure as Example 25 except for notusing masterbatch pellets. The loss factor η of this gear at an ordinarytemperature (24° C.) was 0.008.

EXAMPLE 26

90 parts by weight of modified polyphenylene ether resin (Noryl 731,Japan G.E. Plastic Co., Ltd.) used as base resin and 10 parts by weightof masterbatch pellets G were uniformly blended by a Henschel mixer andinjection molded into a dot printer casing (exterior part). The lossfactor η of this casing at an ordinary temperature (24° C.) was 0.035.

REFERENCE EXAMPLE 3

A dot printer casing was produced by following the procedure of Example26 without using masterbatch pellets. The loss factor η of this casingat an ordinary temperature (24° C.) was 0.010.

                                      TABLE 1                                     __________________________________________________________________________    Production of masterbatch pellets for vibration damper                        __________________________________________________________________________           Binder resin (100 parts by weight)                                       Base resin                                                                                  Content            Content           Content                     ABS resin (% by weight) HIPS resin (% by weight) PC resin (% by            __________________________________________________________________________                                                         weight)                    Ex. 1 -- -- Sumibright M574 50 -- --                                             (Sumitomo Chem.)                                                           Ex. 2 -- -- -- -- -- --                                                       Ex. 3 ABS 15 (JSR*1)) 40 -- -- -- --                                          Ex. 4 ABS 15 (JSR*1)) 40 -- -- -- --                                          Ex. 5 -- -- -- -- Novalex 7025A 50                                                 (*2)                                                                     Ex. 6 -- -- -- -- Novalex 7025A 50                                            Ex. 7 -- -- -- -- -- --                                                       Ex. 8 -- -- -- -- -- --                                                       Ex. 9 -- -- -- -- -- --                                                       Comp. Ex. 1 -- -- Sumibright M574 100 -- --                                      (Sumitomo Chem.)                                                           Comp. Ex. 2 ABS 15 (JSR) 40 -- -- -- --                                     __________________________________________________________________________    Binder resin (100 parts by weight)     Inorganic filler                       Base resin                 SIS resin   Iron compound particles                         Content    Content     Content               Content                                                                            Pellets                                                                         PPE resin (%                                                                by weight) PP                                                                 resin (% by                                                                   weight) Kind                                                                  (% by weight)                                                                 Kind (wt                                                                      parts)             __________________________________________________________________________                                                               No.                                                                            Ex. 1 --  --                                                                 -- -- VS-1 50                                                                 Granular                                                                      magnetite 100                                                                 A                         (Kuraray)  (average particle size: 0.27 μm)                           Ex. 2 -- -- -- -- VS-1 100  Strontium ferrite plates 233 B                         (Kuraray)  (average plate diameter: 1.2 μm)                           Ex. 3 -- -- -- -- VS-1 60 Strontium ferrite plates  60 C                           (Kuraray)  (average plate diameter: 1.2 μm)                           Ex. 4 -- -- -- -- VS-1 60 Magnetite granular (averge 100 D                         (Kuraray)  particle diameter: 0.27 μm)                                Ex. 5 -- -- -- -- VS-1 50 Magnetite granular (averge 100 E                         (Kuraray)  particle diameter: 0.27 μm)                                Ex. 6 -- -- -- -- VS-1 50 Magnetite granular (averge 233 F                         (Kuraray)  particle diameter: 0.27 μm)                                Ex. 7 Noryl 731 50 -- --  VS-1 50 Magnetite plates (averge 100 G                                                                         (*3)                                                                        (Kuraray)                                                                     particle                                                                      diameter: 0.27                                                                μm)                                                                         Ex. 8 Noryl                                                                  731 50 -- --                                                                  VS-1 50                                                                       Magnetite                                                                     granular                                                                      (averge 233 H                                                                       (Kuraray)                                                                 particle                                                                    diameter: 0.27                                                                μm)                                                                         Ex. 9 -- --                                                                  K6014 50 VS-1                                                                 50 Granular                                                                   magnetite                                                                     (averge 100 I                                                                     (Chisso)                                                                  (Kuraray)                                                                     particle                                                                      diameter: 0.27                                                                μm)                                                                         Comp. -- --                                                                  -- -- -- --                                                                   Magnetite                                                                     granular                                                                      (averge 100 J                                                                  Ex. 1                                                                        particle                                                                      diameter: 0.27                                                                μm)                                                                         Comp. -- --                                                                  -- -- VS-1 60                                                                 Magnetite                                                                     granular 400 K       Ex. 2     (Kuraray)  (particle diameter: 0.27 μm)                        __________________________________________________________________________     *1) Produced by Japan Synthetic Rubber Co., Ltd.                              *2) Produced by Mitsubishi Chemical Co., Ltd.                                 *3) Produced by Japan G. E. Plastic Co., Ltd.                            

                  TABLE 2                                                         ______________________________________                                        Formulations for producing vibration damper                                   Masterbatch pellets  Base resin                                                         Content                 Content                                        (parts by  (part by                                                          Kind weight) Kind weight)                                                   ______________________________________                                        Ex. 10                                                                              A       10         HIPS resin 90                                             (Sumibright M574)                                                          Ex. 11 A 20 HIPS resin 80                                                        (Sumibright M574)                                                          Ex. 12 A 10 ABS resin 90                                                         (ABS 15)                                                                   Ex. 13 B 10 ABS resin 90                                                         (ABS 15)                                                                   Ex. 14 C 25 ABS resin 75                                                         (ABS 15)                                                                   Ex. 15 D 7 ABS resin 93                                                          (ABS 15)                                                                   Ex. 16 D 10 ABS resin 90                                                         (AB5 15)                                                                   Ex. 17 E 12.5 PC resin 87.5                                                      (Novalex 7025A)                                                            Ex. 18 F 7 PC resin 93                                                           (Novalex 7025A)                                                            Ex. 19 F 12.5 PC resin 87.5                                                      (Novalex 7025A)                                                            Ex. 20 G 10 PPE resin 90                                                         (Noryl 731)                                                                Ex. 21 H 7 PPE resin 93                                                          (Noryl 731)                                                                Ex. 22 H 10 PPE resin 90                                                         (Noryl 731)                                                                Ex. 23 I 10 PP resin 90                                                          (K 6014)                                                                   Comp. --  -- HIPS resin 100                                                   Ex. 3   (Sumibright M574)                                                     Comp. -- -- ABS resin 100                                                     Ex. 4   (ABS 15)                                                              Comp. -- -- PC resin 100                                                      Ex. 5   (Novalex 7025A)                                                       Comp. -- -- PPE resin 100                                                     Ex. 6   (Noryl 731)                                                           Comp. -- -- PP resin 100                                                      Ex. 7   (K 6014)                                                              Comp. J 10 ABS resin 90                                                       Ex. 8   (ABS 15)                                                              Comp. K 35 ABS resin 65                                                       Ex. 9   (ABS 15)                                                            ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Formulations for producing vibration damper by                                direct kneading                                                                 Binder resin (100 parts by weight)                                                    HIPS resin          PC resin                                                           Content            Content                                    Kind (wt %) Kind (wt %)                                                    ______________________________________                                          Comp. Sumibright M574 97.4 --  --                                             Ex. 10 (Sumitomo Chem.)                                                       Comp. Sumibright M574 98.7 -- --                                              Ex. 11 (Sumitomo Chem.)                                                       Comp Sumibright M574 98.7 -- --                                               Ex. 12 (Sumitomo Chem.)                                                       Comp. Sumibright M574 100 -- --                                               Ex. 13 (Sumitomo Chem.)                                                       Comp. -- --  PC resin 100                                                     Ex. 14   (Novalex 7025A)                                                    ______________________________________                                        Formulations for producing vibration damper by                                  direct kneading                                                               Binder resin (100 parts by weight)                                          PPE resin              SIS resin                                                             Content            Content                                        Kind (wt %) Kind (wt %)                                                    ______________________________________                                          Comp. --  -- VS-1 2.6                                                         Ex. 10   (Kuraray)                                                            Comp. -- -- VS-1 1.3                                                          Ex. 11   (Kuraray)                                                            Comp. -- -- VS-1 1.3                                                          Ex. 12   (Kuraray)                                                            Comp. -- -- -- --                                                             Ex. 13                                                                        Comp. -- -- -- --                                                             Ex. 14                                                                      ______________________________________                                        Formulations for producing vibration damper by                                  direct kneading                                                               Inorganic filler                                                            Iron compound           Mica                                                                    Content            Content                                     Kind (wt parts) Kind (wt parts)                                            ______________________________________                                          Comp. --  -- -- --                                                            Ex. 10                                                                        Comp. -- -- Flaky mica  5.3                                                   Ex. 11   (plate diameter:                                                        150 μm)                                                                 Comp. -- -- Flaky mica 11.1                                                   Ex. 12   (plate diameter:                                                        150 μm)                                                                 Comp. Granular  4.0 -- --                                                     Ex. 13 magnetite                                                               (average particle                                                             diameter: 0.27 μm)                                                        Comp. Strontium 11.1 -- --                                                    Ex. 14 ferrite plates                                                          (average particle                                                             diameter: 1.2 μm)                                                       ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        Composition of vibration damper                                                 Binder resin (100 parts by weight)                                          HIPS resin                ABS resin                                                               Content          Content                                     Kind (parts) Kind (wt %)                                                   ______________________________________                                          Ex. 10 Sumibright M574 97.4 --  --                                             (Sumitomo Chem.)                                                             Ex. 11 Sumibright M574 94.4 -- --                                              (Sumitomo Chem.)                                                             Ex. 12 Sumibright M574  2.6 ABS 15 94.8                                        (Sumitomo Chem.)  (JSR*2))                                                   Ex. 13 -- -- ABS 15 96.8                                                         (JSR)                                                                      Ex. 14 -- -- ABS 15 89.7                                                         (JSR)                                                                      Ex. 15 -- -- ABS 15 97.8                                                         (JSR)                                                                      Ex. 16 -- -- ABS 15 96.8                                                         (JSR)                                                                      Ex. 17 -- -- -- --                                                            Ex. 18 -- -- -- --                                                            Ex. 19 -- -- -- --                                                            Ex. 20 -- -- -- --                                                            Ex. 21 -- -- -- --                                                            Ex. 22 -- -- -- --                                                            Ex. 23 -- -- -- --                                                          ______________________________________                                        Composition of vibration damper                                                 Binder resin (100 parts by weight)                                          PC resin           PPE resin      PP resin                                                  Content        Content      Content                                Kind (wt %) Kind (wt %) Kind (wt %)                                        ______________________________________                                          Ex. 10 --  -- -- -- -- --                                                     Ex. 11 -- -- -- -- -- --                                                      Ex. 12 -- -- -- -- -- --                                                      Ex. 13 -- -- -- -- -- --                                                      Ex. 14 -- -- -- -- -- --                                                      Ex. 15 -- -- -- -- -- --                                                      Ex. 16 -- -- -- -- -- --                                                      Ex. 17 Novalex 96.7 -- -- -- --                                                7025A                                                                        Ex. 18 Novalex 98.9 -- -- -- --                                                7025A                                                                        Ex. 19 Novalex 97.9 -- -- -- --                                                7025A                                                                        Ex. 20 -- -- Noryl 97.4 -- --                                                    731 *4)                                                                    Ex. 21 -- -- Noryl 98.9 -- --                                                    731                                                                        Ex. 22 -- -- Noryl 98.4 -- --                                                    731                                                                        Ex. 23 -- -- -- -- K-6014 97.4                                                     (Chisso)                                                               ______________________________________                                        Composition of vibration damper                                                     Binder resin (100                                                         parts by weight) Inorganic filler                                             SIS resin Iron compound particles                                                          Content                Content                                    Kind (wt %) Kind (wt %)                                                    ______________________________________                                          Ex. 10 VS-1 2.6 Granular magnetite 5.3                                         (Kuraray)  (particle diameter: 0.27 μm)                                   Ex. 11 VS-1 5.6 Granular magnetite 11.1                                        (Kuraray)  (particle diameter: 0.27 μm)                                   Ex. 12 VS-1 2.6 Granular magnetite 5.3                                         (Kurarav)  (particle diameter: 0.27 μm)                                   Ex. 13 VS-1 3.2 Strontium ferrite plates 7.5                                   (Kuraray)  (plate diameter: 1.2 μm)                                       Ex. 14 VS-1 10.3  Strontium ferrite plates 10.3                                (Kuraray)  (plate diameter: 1.2 μm)                                       Ex. 15 VS-1 2.2 Granular magnetite 3.6                                         (Kuraray)  (particle diameter: 0.27 μm)                                   Ex. 16 VS-1 3.2 Granular magnetite 5.3                                         (Kuraray)  (particle diameter: 0.27 μm)                                   Ex. 17 VS-1 3.3 Granular magnetite 6.5                                         (Kuraray)  (particle diameter: 0.27 μm)                                   Ex. 18 VS-1 1.1 Granular magnetite 5.2                                         (Kuraray)  (particle diameter: 0.27 μm)                                   Ex. 19 VS-1 2.1 Granular magnetite 9.6                                         (Kuraray)  (particle diameter: 0.27 μm)                                   Ex. 20 VS-1 2.6 Granular magnetite 5.3                                         (Kuraray)  (particle diameter: 0.27 μm)                                   Ex. 21 VS-1 1.1 Granular magnetite 5.2                                         (Kuraray)  (particle diameter: 0.27 μm)                                   Ex. 22 VS-1 1.6 Granular magnetite 7.5                                         (Kuraray)  (particle diameter: 0.27 μm)                                   Ex. 23 VS-1 2.6 Granular magnetite 5.3                                         (Kuraray)  (particle diameter: 0.27 μm)                                 ______________________________________                                        Composition of                                                                  vibration damper Properties of vibration damper                             Inorganic               Bending                                                 filler  modulus of                                                            Mica  elasticity                                                                            Content  Loss Measured                                                                             Relative                                     (part by factor values values Specific                                       Kind weight) *1) (kgf/cd) (%) gravity                                      ______________________________________                                          Ex. 10 -- -- 0.021 25400 95 1.09                                              Ex. 11 -- -- 0.039 23500 88 1.13                                              Ex. 12 -- -- 0.028 23700 95 1.09                                              Ex. 13 -- -- 0.027 22800 91 1.11                                              Ex. 14 -- -- 0.059 19500 78 1.12                                              Ex. 15 -- -- 0.020 24200 97 1.07                                              Ex. 16 -- -- 0.031 23800 95 1.09                                              Ex. 17 -- -- 0.024 20600 94 1.23                                              Ex. 18 -- -- 0.021 21100 97 1.23                                              Ex. 19 -- -- 0.025 20200 93 1.27                                              Ex. 20 -- -- 0.023 23800 95 1.10                                              Ex. 21 -- -- 0.020 24500 98 1.10                                              Ex. 22 -- -- 0.028 23200 93 1.14                                              Ex. 23 -- -- 0.026 11600 93 0.96                                            ______________________________________                                         *1) Measuring conditions: 24° C., 1 kHz                                *2) JSR: Produced by Japan Synthetic Rubber Co., Ltd.                         *3) Produced by Mitsubishi Chemical Co., Ltd.                                 *4) Produced by Japan G.E. Plastic Co., Ltd.                             

                  TABLE 5                                                         ______________________________________                                        Composition of vibration damper                                                 Binder resin (100 parts by weight)                                          HIPS resin                ABS resin                                                               Content          Content                                      (% by  (% by                                                                 Kind weight) Kind weight)                                                  ______________________________________                                          Comp. Sumibright M574 100    -- --                                            Ex. 3 (Sumitomo Chem.)                                                        Comp. -- -- ABS 15 100                                                        Ex. 4   (JSR*2))                                                              Comp. -- -- -- --                                                             Ex. 5                                                                         Comp. -- -- -- --                                                             Ex. 6                                                                         Comp. -- -- -- --                                                             Ex. 7                                                                         Comp. Sumibright M574  5.3 ABS 15 94.7                                        Ex. 8 (Sumitomo Chem.)  (JSR)                                                 Comp. -- -- ABS 15 94.2                                                       Ex. 9   (JSR)                                                                 Comp. Sumibright M574 97.4 -- --                                              Ex. 10 (Sumitomo Chem.)                                                       Comp. Sumibright M574 98.7 -- --                                              Ex. 11 (Sumitomo Chem.)                                                       Comp. Sumibright M574 98.7 -- --                                              Ex. 12 (Sumitomo Chem.)                                                       Comp. Sumibright M574 100   -- --                                             Ex. 13 (Sumitomo Chem.)                                                       Comp. -- -- -- --                                                             Ex. 14                                                                      ______________________________________                                        Composition of vibration damper                                                 Binder resin (100 parts by weight)                                          PC resin           PPE resin      PP resin                                                  Content        Content      Content                                 (% by  (% by  (% by                                                          Kind weight) Kind weight) Kind weight)                                     ______________________________________                                          Comp. --  -- -- -- -- --                                                      Ex. 3                                                                         Comp. -- -- -- -- -- --                                                       Ex. 4                                                                         Comp Novalex 100 -- -- -- --                                                  Ex. 5 7025A                                                                   Comp -- -- Noryl 100 -- --                                                    Ex. 6   731 *4)                                                               Comp. -- -- -- -- K6014 100                                                   Ex. 7     (Chisso)                                                            Comp. -- -- -- -- -- --                                                       Ex. 8                                                                         Comp. -- -- -- -- -- --                                                       Ex. 9                                                                         Comp. -- -- -- -- -- --                                                       Ex. 10                                                                        Comp. -- -- -- -- -- --                                                       Ex. 11                                                                        Comp. -- -- -- -- -- --                                                       Ex. 12                                                                        Comp. -- -- -- -- -- --                                                       Ex. 13                                                                        Comp. Novalex 100 -- -- -- --                                                 Ex. 14 7025A                                                                ______________________________________                                        Composition of vibration damper                                                      Binder resin  Inorganic filler                                           (100 parts by weight) Iron compound particles                               SIS resin                        Content                                                      Content                (part by                                  Kind (wt %) Kind weight)                                                   ______________________________________                                          Comp. --  -- -- --                                                            Ex. 3                                                                         Comp. -- -- -- --                                                             Ex. 4                                                                         Comp. -- -- -- --                                                             Ex. 5                                                                         Comp. -- -- -- --                                                             Ex. 6                                                                         Comp. -- --  --                                                               Ex. 7                                                                         Comp. -- -- Granular magnetite  5.3                                           Ex. 8   (particle diameter: 0.27 μm)                                       Comp. VS-1 5.8 Granular magnetite 38.9                                        Ex. 9 (Kuraray)  (particle diameter: 0.27 μm)                              Comp. VS-1 2.6 -- --                                                          Ex. 10 (Kuraray)                                                              Comp. VS-1 1.3 -- --                                                          Ex. 11 (Kuraray)                                                              Comp. VS-1 1.3 -- --                                                          Ex. 12 (Kuraray)                                                              Comp. -- -- Granular magnetite  4.0                                           Ex. 13   (particle diameter: 0.29 μm)                                      Comp. -- -- Strontium ferrite plates 11.1                                     Ex. 14   (plate diameter: 1.2 μm)                                        ______________________________________                                        Composition of                                                                  vibration damper Properties of vibration damper                             Inorganic               Bending                                                 filler  modulus of                                                            Mica  elasticity                                                                            Content  Loss Measured                                                                             Relative                                     (part by factor values values Specific                                       Kind weight) *1) (kgf/cd) (%) gravity                                      ______________________________________                                          Comp. -- -- 0.009 26700 100  1.05                                             Ex. 3                                                                         Comp. -- -- 0.010 25000 100  1.05                                             Ex. 4                                                                         Comp. -- -- 0.008 21800 100  1.19                                             Ex. 5                                                                         Comp. -- -- 0.010 25000 100  1.06                                             Ex. 6                                                                         Comp. -- -- 0.012 12500 100  0.90                                             Ex. 7                                                                         Comp. -- -- 0.011 26100 98 1.09                                               Ex. 8                                                                         Comp. -- -- 0.050 15100 60 1.50                                               Ex. 9                                                                         Comp. -- -- 0.013 25300 95 1.05                                               Ex. 10                                                                        Comp. Flaky mica  5.3 0.012 26500 99 1.08                                     Ex. 11 (plate                                                                  diameter:                                                                     150 μm)                                                                   Comp. Flaky mica 11.1 0.013 23500 88 1.11                                     Ex. 12 (plate                                                                  diameter:                                                                     150 μm)                                                                   Comp. -- -- 0.010 26000 97 1.08                                               Ex. 13                                                                        Comp. -- -- 0.008 21500 99 1.29                                               Ex. 14                                                                      ______________________________________                                         *1) Measuring conditions: 24° C., 1 kHz                                *2) JSR: Produced by Japan Synthetic Rubber Co., Ltd                          *3) Produced by Mitsubishi Chemical Co., Ltd.                                 *4) Produced by Japan G.E. Plastic Co., Ltd.                             

What is claimed is:
 1. A cartridge half, cassette half or disk shellmade of a damping material having a loss factor of not less than 0.015at 24° C., a relative bending modulus of not less than 70% based on abending modulus of a damping material consisting of the base resin, anda specific gravity of 0.95 to 1.30, said damping material consistingessentially of:100 parts by weight of a binder resin comprising 85 to99% by weight of at least one base resin selected from the groupconsisting of polypropylenes, polystyrenes,acrylonitrile-butadiene-styrene copolymers, polycarbonates,polyphenylene ethers and modified polyphenylene ethers, and 1 to 15% byweight of styrene-isoprene-styrene block copolymer having anumber-average molecular weight of 30,000 to 300,000, and 1 to 20 partsby weight, based upon 100 parts by weight of the binder resin, of ironcompound particles having particle size of 0.05 to 10 μm and selectedfrom the group consisting of hematite particles, maghemite particles,magnetite particles, berthollide compound particles, barium ferriteparticles, strontium ferrite particles, goethite particles, akaganeiteparticles and lepidocrocite particles.
 2. A cartridge half, cassettehalf or disk shell according to claim 1, wherein the base resin is atleast one resin selected from the group consisting of polystyrenes,acrylonitrile-butadiene-styrene copolymers, polycarbonates,polyphenylene ethers and modified polyphenylene ethers.
 3. A cartridgehalf, cassette half or disk shell according to claim 1, wherein thecontent of the base resin is 88 to 98% by weight, the content ofstyrene-isoprene-styrene block copolymer is 2 to 12% by weight, and thecontent of iron compound particles is 3 to 20 parts by weight based on100 parts by weight of the binder resin.
 4. A method of using a dampingmaterial having a loss factor of not less than 0.015 at 24° C., arelative bending modulus of not less than 70% based on a bending modulusof a damping material consisting of the base resin, and a specificgravity of 0.95 to 1.30, said method comprising the step of forming saiddamping material into a cartridge half, cassette half or disk shell,said damping material consisting essentially of:100 parts by weight of abinder resin comprising 85 to 99% by weight of at least one base resinselected from the group consisting of polypropylenes, polystyrenes,acrylonitrile-butadiene-styrene copolymers, polycarbonates,polyphenylene ethers and modified polyphenylene ethers, and 1 to 15% byweight of styrene-isoprene-styrene block copolymer having anumber-average molecular weight of 30,000 to 300,000, and 1 to 20 partsby weight, based upon 100 parts by weight of the binder resin, of ironcompound particles having particle size of 0.05 to 10 μm.